PROJECT SUMMARY/ABSTRACT: More than one-third of adults over age 60 have obesity and 50% have prediabetes. The Diabetes Prevention Program (DPP) clinical trial demonstrated that a behavioral lifestyle intervention could reduce the incidence of type 2 diabetes and lead to clinically significant weight loss, particularly among older adults. Several studies have examined how to translate DPP into community- based settings and primary care, but these have been limited by small sample sizes, absence of a control group, and very few older adults. Larger, higher-quality pragmatic studies are needed to determine how to translate these findings into practice. Recently, YMCA demonstrated that DPP could be successfully delivered to Medicare beneficiaries with prediabetes and lead to clinically significant weight loss and cost savings. Based on these findings, starting in January 2018 the Centers for Medicare & Medicaid Services (CMS) plans to cover a 12-month DPP program for Medicare beneficiaries. Yet, the feasibility of implementing this program at the required scale remains unclear. While Medicare will fund DPP in-person or online, the reach and effectiveness of either format among older adults needs to be determined. Further, we have limited knowledge about the behavioral and psychosocial factors that influence program engagement in this group. We propose to rigorously evaluate the implementation of Medicare DPP at Kaiser Permanente Northwest (KPNW), a large, integrated health care system, to determine the feasibility and effectiveness of delivering DPP in-person or online. KPNW will implement the 12-month Medicare DPP in 2017, and will randomize 6000 beneficiaries at high risk for type 2 diabetes to one of four treatment arms: 1) DPP in-person; 2) DPP online; 3) patient choice between DPP in-person or online; or 4) Usual care. We will examine program reach (comparing in-person and online formats on recruitment and retention rates and session attendance), compare treatment arms on clinical measures (weight and HbA1c extracted from the electronic health records), and examine factors associated with program effectiveness and engagement. We will also compare the four treatment arms on change in dietary intake and minutes of physical activity at six and 12 months, as well as on measures of depression, quality of life, stress, social support, and motivation at baseline and at six months. Qualitative interviews will be conducted to explore factors associated with program enrollment, satisfaction, and continued participation. Finally, we will compare the cost-effectiveness of DPP in-person, DPP online, and DPP choice. In short, this pragmatic study will determine the best, most cost-effective methods for delivering these services to this high risk Medicare population.